Thus far, there have been roughly two types of fin attachment structure of surfboard: a fixed fin type and a detachable fin type. Compared to a fixed fin type, a detachable fin type is used more frequently. There are various attachment structures because it allows the attachment of a fin of an arbitrary shape according to a user's preference and the fin can be detached and carried.
That is, a fin box etc. is arranged in advance on the bottom surface of a surfboard by embedding it, and then the fin is detachably mounted in the fin box. In this case, structures that allow a fin to be detachable and incorporate so-called screw fixing include those disclosed in Japanese Publication of Patent Application (Kokai) No. H6-255575 (patent document 1), Translated Japanese Publication of Patent Application No. 2001-520961 (patent document 2), Translated Japanese Publication of Patent Application No. 2002-530242 (patent document 3), and Japanese Unexamined Patent Publication (Kokai) No. 2003-306195 (patent document 4).
These have a structure m which screws, bolts, etc., are used to fasten a fan to the fin box. In addition, the structure bas 6rrooves in the fin box by which the fin is fastened into the fin box according to those disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2005-74026 (patent document 5), Japanese Unexamined Patent Publication (Kokai) No. 2005-112206 (patent document 6), and Japanese Unexamined Patent Publication (Kokai) No. 2006-280839 (patent document 7).
Further, the structure in which the fin is fastened using a C-shaped clamp is disclosed in Translated Japanese Publication of Patent Application No. 2003-528003 (patent document 8). In addition to the above, structures in which the fin is fastened so that it can be attached in an easily detachable manner using a special locking member include those disclosed in Translated Japanese Publication of Patent Application No. 2005-508798 (patent document 9) and Translated Japanese Publication of Patent Application No. 2005-526664 (patent document 9). Furthermore, the structure in which both the fin box and the fin fitted therein has a fitting structure in a special shape so that the fin can be fastened in an easily detached manner is one disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2007-16969 (patent document 11).